A conveyor robot or the like is used for supplying and removing a material to and from a substrate processing device and the like. FIG. 1 shows a vacuum suction pad 1 of a first conventional example for conveying a substrate for use in a vacuum suction device of the conveyor robot, and a liquid crystal panel 2, which is a laminated substrate formed by bonding substrates to be sucked together. As is well known, the liquid crystal panel 2 is formed in such a manner that, after two glass substrates 3a and 3b are superposed with particulate spacers 4 interposed therebetween, peripheral edges of the glass substrates 3a and 3b are fixed by using an adhesive (sealant) 5, followed by injection of liquid crystal through a pore provided in a layer of the adhesive (sealant) 5. The vacuum suction pad 1 includes a rubber suction disk 1a formed like an upside down bowl and a suction tube 1b provided in a penetrating position through the top of the suction disk 1a. 
FIG. 2 shows a state where a lower edge peripheral portion 1c of the suction disk 1a is brought into press-contact with an upper surface of the liquid crystal panel 2 to perform vacuum suction through the suction tube 1b. By this vacuum suction, a vacuum-sucked place of the upper glass substrate 3a might be locally deformed upward to cause an increase in a gap between the upper and lower glass substrates in this place, thereby temporally lowering pressure. In this case, the liquid crystal flows, as if concentrated, into this place. The spacers 4 with a diameter of, for example, 5 to 10 μm are inserted so as to have a uniform density of about 100 particles/mm2. However, being unfixed to the glass substrates 3a and 3b, the spacers 4 move along with the movement of the liquid crystal. When no liquid crystal has been injected into the liquid crystal panel 2, air flow into a place where pressure has been lowered. In this case, because the resistance to the movement of the spacers 4 is small, the movement of the spacers 4 is further contributed.
Consequently, after the suction by the vacuum suction pad 1, dispersion in the distribution of the spacers 4 has occurred, and corresponding to this dispersion, variations in the gap between the upper and lower glass substrates have occurred, as shown in FIG. 3. Further, although not shown in the figure, there recently exists a liquid crystal panel of the type obtained by bonding two glass substrates together without spacers, and this spacer-free type liquid crystal panel is configured in a state where the spacers 4 are not inserted into the liquid crystal panel 2 in FIGS. 1 to 3. Also in the case this spacer-free type liquid crystal panel is vacuum-sucked by the suction disk 1a, the upper glass substrate 3a is locally deformed upward, and once deformed, it does not changed back into the original form, thereby causing variations in the gap between the upper and lower glass substrates. If the gap between the upper and lower glass substrates of the liquid crystal panel varies by 0.04 mm or more, a color shading appears on the display surface, with which the liquid crystal panel becomes defective as a product.
As thus described, in the first conventional example, the deformation of the upper glass substrate occurs when the vacuum suction pad 1 vacuum-sucks the liquid crystal panel 2, caused by too large a diameter of the suction disk 1a as compared to the thickness of the glass substrate and the size of the spacer 4. The diameter of the suction disk 1a is several tens of mm while the thickness of the glass substrate is 0.5 to 1.1 mm, and a thin glass substrate tends to be selected.
In the vacuum suction pad 1 of FIG. 1, suction force becomes insufficient if the size of the suction disk 1a is reduced for the purpose of avoiding the problems of the local deformation of the suction surface of the glass substrate, the variations in the gap between the glass substrates due to the suction by the vacuum suction pad 1 and the problem of the dispersion in the distribution, which results from the local deformation and the variations in the gap, of the spacers 4. To this end, as shown in FIG. 4, there is a method for providing a plurality of vacuum suction pads 1 each having a small suction disk to suck the liquid crystal panel 2. In this case, it is necessary to attach all the vacuum suction pads 1 to the vacuum suction device such that the suction surface of each of the vacuum suction pads 1 is provided within a prescribed attachment tolerance range in order to prevent the vacuum suction pads 1 from pressing the glass substrate surface. Further, also in the case the liquid crystal panel 2 to be sucked is swollen or bent, it is necessary to set the suction surface of each of the vacuum suction pads 1 within a clearance at which the suction of the liquid crystal panel 2 is possible.
If the plurality of vacuum suction pads 1 are attached to the vacuum suction device with the suction surfaces thereof out of the above-mentioned attachment tolerance range, the liquid crystal panel 2 is conveyed while imperfectly sucked, whereby the liquid crystal panel 2 might drop when conveyed, or might be pressed by the vacuum suction pad 1 when sucked to cause occurrence of variations in the gap between the upper and lower glass substrates, leading to occurrence of product defect.
FIG. 5 is an exploded view showing a structure of a vacuum suction pad 21 in a second conventional example, shown in JP-A 11-019838. A suction disk 22 of the vacuum suction pad 21 is formed into a disk shape and is made of a photosensitive resin material, a central portion of which is provided with a vertically penetrating suction port 22c, and a suction surface of the suction disk 22 is provided with a large number of protruded portions and recessed portions, as described later. These large number of protruded portions and recessed portions are formed by etching the photosensitive resin material.
FIG. 6 shows the structure of the suction surface of the suction disk 22 in the vacuum suction pad 21, and FIG. 7 shows a cross-sectional view of the vacuum suction pad 21. The suction disk 22 has an airtight part 22a at a peripheral portion thereof with a flat surface, and a suction part 22b where a large number of protruded portions and recessed portions are formed. As shown in FIG. 7, a reinforcement layer 23 is a layer made of a large rigid plate material so as to prevent the photosensitive resin material from being deformed due to an external stress, and is bonded to the photosensitive resin material in the stage of manufacturing the photosensitive resin material into a plate-making material. A magnet sheet 24 is a sheet with the same diameter as that of the suction disk 22. A double-faced adhesive sheet 25 is an adhesive sheet for joining the magnet sheet 24 and the reinforcement sheet 23 together, and has the same diameter as that of the suction part 22b on the suction disk 22. A hole Q is formed in a position corresponding to the suction port 22c, in each of those members 23 to 25.
In the case of making the diameter of the double-faced adhesive sheet 25 equivalent to the diameter of the suction part 22b, as shown in FIG. 7, only the suction part 22b on the suction disk 22 is fixed to a supporting member 26 via the magnet sheet 24. Meanwhile, the airtight part 22a is not fixed and stays free. FIG. 8 shows an example where the diameter of the double-faced adhesive sheet 25 is made equivalent to that of the suction disk 22, and in this case, the whole surface of the suction disk 22 is fixed to the supporting member 26.
Turning back to FIG. 6, an expanded view X of the peripheral portion of the suction disk 22 is referred to. The airtight part 22a is a region where the photosensitive resin material is not etched. In the suction part 22b, a large number of small-circular regions are non-etching portions (protruded portions) and the regions other than the protruded portions are etching portions (recessed portions). As shown in the expanded view X in FIG. 6, the small circular places are left as protruded portions M and the other places become recessed portions N. Herein, the protruded portions M and the airtight part 22a are both non-etching portions and thus positioned on the same surface.
The supporting member 26 is an iron material having the same diameter as that of the magnet sheet 24, and a supporting part 26a is integrally formed at a central portion corresponding to the suction port 22c of the suction disk 22. A suction tube 27 is inserted through the supporting part 26a and is connected to a vacuum pump (not shown). The suction disk 22 is integrally joined with the reinforcement layer 23, the double-faced adhesive sheet 25 and the magnet sheet 24, and is made attachable to/detachable from the supporting member 26 by the action of the magnet sheet 24.
When the vacuum suction pad 21 as thus configured is brought into press-contact with the flat liquid crystal panel 2, the recessed portions N in the suction part 22b on the suction disk 22 form closed spaces with the airtight part 22a, and since the protruded portions M are independent of one another, the suction port 22c of the suction disk 22 is communicated with the closed spaces as shown in FIG. 5, whereby the vacuum suction is performed using the foregoing vacuum pump (not shown) through the suction port 22c, allowing the suction disk 22 to be sucked to the liquid crystal panel 2.
FIG. 9 is a cross-sectional view showing a state of sucking a liquid crystal panel 2 having a small outer shape with the use of the foregoing vacuum suction pad 21 of the second conventional example. In this case, in order to hold the substrate, one vacuum suction pad 21 is used for the vacuum suction device to be installed in a conveyor robot or the like, and the size of the liquid crystal panel 2 is in such a degree as to be slightly larger than that of the vacuum suction pad 21. When the liquid crystal panel 2 is made to be sucked by the vacuum suction pad 21, the large number of protruded portions M formed on the same surface as the airtight part 22a in the expanded view X of FIG. 6 are brought into contact with the upper surface of the upper glass substrate 3a in the liquid crystal panel 2, which can prevent local deformation of the upper glass substrate 3a in the liquid crystal panel 2, and hence variations in the gap between the upper glass substrate 3a and the lower glass substrate 3b does not occur. Moreover, also in the case of the liquid crystal panel of which the gap is formed without insertion of the spacers, no variations in the gap between the upper and lower glass substrates occur. It should be noted that, in the case the suction disk 22 itself is sufficiently flexible, the vacuum suction pad 21 may be a vacuum suction pad of the type obtained by fixing the whole surface of the suction disk 22 with the double-faced adhesive sheet 25, as shown in FIG. 8.
In the case the liquid crystal panel for use in individual display devices has a small shape, a mother liquid crystal panel is segmented to manufacture a plurality of liquid crystal panels of a prescribed size. An example of such a panel is a liquid crystal panel to be used for mobile phones, personal digital assistances (PDAs) and the like. On the other hand, in the case of a liquid crystal panel having a large outer shape, a plurality of vacuum suction pads are used as in the vacuum suction devices shown in FIG. 4.
In the case one vacuum suction device is provided with a plurality of vacuum suction pads, when the vacuum suction pad 1 of the first conventional example is used as shown in FIG. 4, as described above, in the liquid crystal panel, the local deformation of the upper glass substrate occurs and dispersion in the distribution of the foregoing spacers occurs caused by the local deformation, to bring about occurrence of product defect. For this reason, the vacuum suction pad 21 of the second conventional example is used.
There exists a distance (clearance) at which the vacuum suction pad can suck the liquid crystal panel. In the vacuum suction pad 21 having the structure shown in FIG. 5, air is discharged through the suction tube 27. At this time, the vacuum suction pad 21 sucks the air in front thereof so as to suck the liquid crystal panel. A distance from the surface of the upper glass substrate in the liquid crystal panel to the suction disk 22 of the vacuum suction pad 21 at this time is referred to as a clearance at which the suction is possible. The conventional clearance is 0.0 to 0.3 mm, and since the adequate range is very narrow, it has been very difficult to maintain the clearance and also to adjust the same.
As shown in FIGS. 10(a) and (b), with the liquid crystal panel 2 swollen or bent, even if a plurality of vacuum suction pads 21 are provided in the vacuum suction device within a prescribed attachment tolerance range, there have been cases where the clearance G between the upper surface of the liquid crystal panel 2 and the vacuum suction pad 21 exceed the clearance at which the suction of the vacuum suction pad 21 is possible. In such a case, any one of the plurality of vacuum suction pads 21 cannot suck the liquid crystal panel 2 in a regular state, and the liquid crystal panel 2 is conveyed while imperfectly sucked, which might result in that the liquid crystal panel 2 drops when conveyed, or since the vacuum suction pad 21 presses the liquid crystal panel 2 in sucking the liquid crystal panel 2, the upper glass substrate in the liquid crystal panel 2 is locally deformed to lead to occurrence of variations in the gap between the upper and lower glass substrates.
The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a vacuum suction head, comprising a vacuum suction pad which can hold a substrate being swollen or bent without making the substrate defective, widen a clearance between the vacuum suction pad and the substrate at which the suction is possible during the suction, and prevent local deformation of the substrate due to the suction as well as preventing occurrence of variations in the gap between the upper and lower glass substrates caused by the local deformation in the case of the laminated substrate such as a liquid crystal panel.